Abstract-Inverse magneto-refraction as a mechanism for laser modification of spin-spin exchange parameters and subsequent terahertz emission from iron oxides

R. V. Mikhaylovskiy, E. Hendry, A. Secchi, J. H. Mentink, M. Eckstein, A. Wu, R. V. Pisarev, V. V. Kruglyak, M. I. Katsnelson, Th. Rasing, A. V. Kimel

(Submitted on 22 Dec 2014)

Inverse magneto-refraction as a mechanism for laser modification of spin-spin exchange parameters and subsequent terahertz emission from iron oxides

Ultrafast non-thermal manipulation of magnetization by light relies on either indirect coupling of the electric field component of the light with spins via spin-orbit interaction or direct coupling between the magnetic field component and spins. Here we propose a novel scenario for coupling between the electric field of light and spins via optical modification of the exchange interaction, one of the strongest quantum effects, the strength of which can reach 1000 Tesla. We demonstrate that this isotropic opto-magnetic effect, which can be called the inverse magneto-refraction, is allowed in a material of any symmetry. Its existence is corroborated by the experimental observation of THz emission by magnetic-dipole active spin resonances optically excited in a broad class of iron oxides with a canted spin configuration. From its strength we estimate that a sub-picosecond laser pulse with a moderate fluence of ~ 1 mJ/cm^2 acts as a pulsed effective magnetic field of 0.01 Tesla, arising from the optically perturbed balance between the exchange parameters. Our findings are supported by a low-energy theory for the microscopic magnetic interactions between non-equilibrium electrons subjected to an optical field which suggests a possibility to modify the exchange interactions by light over 1 %.

Subjects:	Strongly Correlated Electrons (cond-mat.str-el); Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
Cite as:	arXiv:1412.7094 [cond-mat.str-el]
	(or arXiv:1412.7094v1 [cond-mat.str-el] for this version)

Submission history

From: Rostislav Mikhaylovskiy [view email]
[v1] Mon, 22 Dec 2014 18:55:13 GMT (2198kb)

Abstract-Terahertz emission spectroscopy of laser-induced spin dynamics in TmFeO3 and ErFeO3 orthoferrites

R. V. Mikhaylovskiy, E. Hendry, V. V. Kruglyak, R. V. Pisarev, Th. Rasing, and A. V. Kimel
http://journals.aps.org/prb/abstract/10.1103/PhysRevB.90.184405

Using the examples of laser-induced spin-reorientation phase transitions in TmFeO3 and ErFeO3 orthoferrites, we demonstrate that terahertz emission spectroscopy can obtain novel information about ultrafast laser-induced spin dynamics, which is not accessible by more common all-optical methods. The power of the method is evidenced by the fact that, in addition to the expected quasi-ferromagnetic and quasi-antiferromagnetic modes of the iron sublattices, terahertz emission spectroscopy enables detection of a resonance optically excited at an unexpected frequency of ∼0.3–0.35 THz. By recording how the amplitude and phase of the excited oscillations depend on temperature and applied magnetic field, we show that the unexpected mode has all the features of a spin resonance of the Fe3+ ions. We suggest that it can be assigned to transitions between the multiplet sublevels of the 6A1 ground state of the Fe+3ions occupying rare-earth positions.

DOI: http://dx.doi.org/10.1103/PhysRevB.90.184405

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• Published 5 November 2014
• Received 22 July 2014
• Revised 23 September 2014

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